1. Field of the Invention
The present invention relates to a head mounted display (HMD) and an optical position adjustment method of the head mounted display.
2. Description of the Related Art
A virtual image display device (image display device) is well known, for example, from Japanese Patent Laid-Open No. 2006-162767 that is designed to allow for the viewer to view a two-dimensional image, formed by an image forming device, as an enlarged virtual image by means of a virtual image optics.
As illustrated in a conceptual diagram shown in FIG. 1, an image display device 100 includes an image forming device 111, collimating optics 112 and optical device (light guiding section) 120. The image forming device 111 includes a plurality of pixels arranged in a two-dimensional matrix. The collimating optics 112 shapes light, emitted from the pixels of the image forming device 111, into parallel beams. The optical device 120 receives light shaped into parallel beams by the collimating optics 112, guides the beams therein and emits them. The optical device 120 includes a light guide plate 121, first deflection section 130 (e.g., made up of a single layer of an optical reflecting film) and second deflection section 140 (e.g., made up of a multi-layer optical reflecting film having a multi-layer stacked structure). The light guide plate 121 emits incident light that has propagated therein by total reflection. The first deflection section 130 reflects incident light on the light guide plate 121 in such a manner that incident light is totally reflected in the light guide plate 121. The second deflection section 140 causes light, that has propagated in the light guide plate 121 by total reflection, to be emitted from the light guide plate 121. When used to make up an HMD, the image display device 100 configured as described above contributes to reduced weight and size of the HMD.
Alternatively, a virtual image display device (image display device) using a holographic diffraction grating is well known, for example, from Japanese Patent Laid-Open No. 2007-94175 that is designed to allow for the viewer to view a two-dimensional image, formed by an image forming device, as an enlarged virtual image by means of a virtual image optics.
As illustrated in a conceptual diagram shown in FIGS. 12A and 12B, an image display device 300 basically includes the image forming device 111 and collimating optics 112 and an optical device (light guiding section) 320 adapted to receive light displayed on the image forming device 111 for displaying an image and guide it onto an eye 41 of the viewer. Here, the optical device 320 includes a light guide plate 321 and first and second diffraction grating members 330 and 340 each made up of a reflection volume holographic diffraction grating provided on the light guide plate 321. The collimating optics 112 receives light emitted from the pixels of the image forming device 111 and shapes it into parallel beams which are then received by the light guide plate 321. The parallel beams strike a first surface 322 of the light guide plate 321 and are emitted therefrom. On the other hand, the first and second diffraction grating members 330 and 340 are attached to a second surface 323 of the light guide plate 321 that is parallel to the first surface 322 thereof.
Still alternatively, a stereoscopic display is well known from Japanese Patent Laid-Open Nos. Hei 08-322004 and Hei 08-211332 that is designed to display, on the display surface of the display section, an image in such a manner as to permit stereoscopic viewing. The stereoscopic display device disclosed in Japanese Patent Laid-Open No. Hei 08-322004 includes a section adapted to electrically move the image displayed on the display device horizontally so that the convergence angle roughly matches the visibility in real time. On the other hand, the stereoscopic image reproduction device disclosed in Japanese Patent Laid-Open No. Hei 08-211332 is designed to provide a stereoscopic image by taking advantage of binocular parallax and includes a convergence angle selection section and control section. The convergence angle selection section sets the convergence angle for viewing a reproduced image. The control section controls the relative reproduction positions of the left and right images based on the information about the selected convergence angle.